Pneumatic hammer.



Patented Sept 5, I899 W N N Q N\ f 0 0 $N mm N y 0 m 2 Mum mm a N m Nwmw W PM \U N W 5 w i m a m. C G W 6 N M I %Wf NITED STATES PATENTOFFICE,

ELIAS GUNNELL, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TO W. IRVINGBABOOOK, OF SAME PLACE.

PNEUMATIC HAMMER.

SPECIFICATION forming part of Letters Patent No. 632,261, datedSeptember 5, 1899. 7

Application filed March 6, 1899.

To all whom it may concern.-

Be it known that I, ELIAs GUNNELL, a citizen of the United States,residing at Chicago, in the county of Cook, State of Illinois, haveinvented certain new and useful Improvements in Pneumatic Hammers, ofwhich the following is a description, reference being had to theaccompanying drawings, forming a part of this specification.

My invention relates to the engine part of such hammers; and it consistsin a certain novel construction, arrangement, and operation of the Valvefor controlling the inlet and exhaust of the motive fluid at the rearend of the piston-chamber.

In the drawings I have illustrated the hammer as adapted for use as apneumatic riveter, the cylinder having cast upon its upper side asocket-piece by which it is adapted to be secured to a dependent arm ofthe riveter-frame; but the device is adapted to any of the uses of apneumatic hammer and may be provided with a handle and used as ahand-tool or be supported in any suitable manner and by any suitablemeans.

Figure 1 is a longitudinal vertical section of the machine with thepiston at the rear end of the piston-chamber, and Fig. 2 a correspondingview with the piston at the forward end of its stroke and ready to beginits backward stroke.

Same letters of reference are used to indicate identical parts in thetwo views.

A is the cylinder, which in the present instance, as above stated, hasformed upon its upper side a socket-piece B for attachment to ariveter-frame, but which will be omitted if the hammer is to be used asa hand-tool or otherwise supported. The rear end of the cylinder A isclosed by a screw-plug or cyl inder-head O, and its front end has driveninto it the usual sleeve or bushing D, adapted to receive the shank orstem E of the rivet-set or other working tool. The interior of thiscylinder A is bored to form a piston-chamber proper of two diameters inwhich fits and travels the piston, composed of the body portion F,fitting the smaller bore of the pistonchamber, and the head F, at therear end of the body portion F and fitting the larger bore of thepiston-chamber.

The reduced diam- Serial No. 708,028. N model.)

eter of the bodyportion F of the piston leaves the latter surrounded inthe larger bore of the piston-chamber by an annular chamber G in frontof the pistonhead F. The n10- tive fluid is constantly admitted (whenthe main throttle-valve is open) to this chamber G through the maininlet-passage II and acts upon the annular front end of the pistonhead Fand tends to constantly press the piston rearward, the piston beingreciprocated by the alternate admission and exhaust of the motive fluidto the larger rear end of the piston-head F. The valve for controllingthis admission and exhaust of the motive fluid at the rear end of thepiston-chamber is located within the piston itself, to which end thelatter is provided in its rear half with a central longitudinal bore orchamber I, whose extreme forward end has a reduced diameter, forming anannular shoulder in the chamber at Ct. chamber is interiorly threadedand has screwed into it a flanged plug J, having a central bore ofconsiderably less diameter than the central bore or chamber I, formed inthe piston, with the result that there is thus formed in the piston alongitudinal valvechamber composed of a middle portion of maximumdiameter, a forward portion of less diameter, and arearward portion ofstill less diameter. Fitting in the chamber thus formed is the tubularvalve, composed of a middle portion or head K, fitting the largestdiameter of the valve-chamber, a forward portion K, fitting the forwardportion of the valve-chamber, and a rear portionK, fitting the rearportion of the valve-chamber. The forward side of the middle head K ofthis valve thus presents an annular pressure area corresponding to theshoulder a in the Wall of the chamber, and its rear side presents alarger annular pressure area, corresponding to the difference in thediameter between the middle portion of the valve-chamber and the reducedrear portion thereof.

The motive fluid is constantly admitted to the forward pressure area ofthe valv'ethrough a passage L, (shown in dotted lines,) extendingthrough the shell of the piston around the valve-chamber and opening atits outer end into the pressure-chamber G, with the result The rear endof this central bore or that a constant rearward pressure is exertedupon the valve, which pressure is intermittently overcome and the valveforced forward in its chamber by the admission of the motive fluid tothe annular rear side of the middle head K of the valve through themedium of a longitudinal passage M, formed in the piston F and providedwith an outwardlyopening port I) at its forward end and at its rear endwith an inwardly-opening port connecting it with the rear end of thelarge middle portion of the valve-chamber. Asecond longitudinal passageN, formed in the piston F at its opposite side, opens at its front endthrough the forward end of the piston and at its rear end communicateswith the reduced forward portion of the valve-chamber. A seriesofdiagonal ports orlpassages, 0 extending through the piston-head F andplug J, furnish communication between the pressurechamber G and thecentral bore of the piston and the rear end of the piston-chamber. Theinterior of the cylinder A in front of the piston F is constantly opento the atmosphere through a port P, so that the longitudinal passage Nin the piston F constitutes an exhaust-passage whose forwardvend isalways open to the atmosphere and whose rear end is alternately openedand closed by the part K of the valve. The front end of the piston-chamber proper or of the portion which fits and guides the body F ofthe piston ter minates at the shoulder 0, forward of which the internalbore of the cylinder is slightly enlarged to form an exhaust-chamberaround the body F of the piston when the latter is at the forward end ofits stroke.

The operation of the machine under the above-described construction andarrangement of parts is as follows: In the position of the parts shownin Fig. 1 the valve will be held in its forward position, as thereshown, by the pressure admitted to the rear side of its middle head Kthrough the passage M, and in such forward position of the valve therear end of the exhaust-passage N will be closed and the inner ends ofthe ports 0 will be uncovered and free communication established betweenthe pressure-chamber G and the rear end of the piston-chamber, with theresult that the motive fluid thus admitted behind the piston will drivethe latter forward. As soon as the port B, at the front end of thepassage M, passes from the larger bore to the smaller bore of thepiston-chamber it will be closed and the admission of motive fluid tothe rear side of the valve be thereby cut off, so that during thefurther forward movement of the piston the valve will be held in itsforward position, Fig. 1, by the motive fluid confined in the middleportion of the valve-chamher behind it. As soon, however, as the port 1)passes beyond the forward end of the piston-chamber proper and clearsthe shoulder a the passage M and the middle portion of the valve-chamberwill be opened to the exhaust, with the result that the constantpressure admitted to the forward side of the valve (through the passageL) will drive the valve rearward in its chamber in the piston, causingits rear portion K to cover the inner ends of the port 0 and cut off themotive fluid from the chamber behind the piston, while its forwardport-ion K will uncover the rear end of the exhaust-passage N, and thusplace the chamber behind the piston in communication (through thecentral bore in the piston and valve) with the exhaust, (see Fig. 2,)where upon the pressure of the motive fluid in the chamber G, constantlyexerted against the annular forward shoulder of the piston-head F, willdrive the piston rearward again. During this rearward movement of thepiston as soon as the port I) at the front end of the passage M passesinto the larger bore G of the piston-chamber the motive fluid will beadmitted through said passage to the rear side of the valve and there,acting against the larger pressure area of the valve, will drive thelatter forward again against the constant pressure admitted through thepassage L to its forward side. This forward movement of the valve. inits chamber as the piston approaches the rear end of its strokewillclose the rear end of the exhaust-passage N and open the rear ends ofthe inlet ports or passages O, thereby again admitting the motive fluidfrom the pressure-chamber G to the rear end of the piston-chamber,behind the piston, cushioning the latter at the end of its rearwardstroke and then driving it forward again, as before.

I have shown leather rings cl and d at the front end of the valvechamber and between the rear side of the head R of the valve and therear wall of the middle portion of the valvechamber to cushion the valveat the opposite ends of its strokes and to form tighter joints; but theyare not essential.

It will be understood from the foregoing clescription that I employ adifferential piston to whose smaller pressure area the motive fluid isconstantly admitted and to whose larger pressure area the motive fluidis alternately admitted and exhausted by the operation of a differentialvalve carried by the piston, and to whose smaller area the motive fluidis constantly admitted from the larger piston-chamber and to whoselarger pressure area the motive fluid is alternately admitted andexhausted through a passage placed in communication with'themotive-fluid supply at one end of the piston-stroke and with the exhaustat the opposite end of the pistonstroke. I am aware that differentialpistons have before been employed in pneumatic hammers and that theadmission and exhaust of the motive fluid behind the piston has beencontrolled by a valve carried by the piston and located in alongitudinal central bore therein; but so far as I am aware theconstruction and arrangement of my valve and piston and their mode ofcooperation with each other are novel and an improvement upon thoseheretofore employed. The construction of both valve and piston is exceedingly simple and of such character that the Work may be readily done bythe ordinary machinist Without especial skill in the construction ofthis particular class of tools. None of the parts are of delicateconstruction or apt to break or get out of order, While access to thevalve-chamber for inspection or removal of the valve, if occasion shouldrequire, may be readily had by removing the piston from the cylinder andunscrewing the plug J.

Having thus fully described my invention, I claim 1.Inapneumatichammer,thecombination of a cylinder bored to form apiston-chamber of two diameters, a differential piston in said chamber,and a differential valve located in the chamber formed by a centrallongitudinal bore in the rear end of the piston, the motive fluid beingconstantly admitted to the smaller pressure area of said valve, andalternately admitted to and exhausted from its larger pressure areathrough a passage placed in communication With the motive-fluid supplyat one end of the piston-stroke and with the exhaust at the opposite endof the pistonstroke, and the movements of said valve in its chamberserving to place the rear end of the piston-chamber alternately incommunication With the motive-fluid supply and with the exhaust,substantially as described.

2. The combination of the cylinder bored to form a piston-chamber of tWodiameters, a differential piston therein, and a diiferential tubularvalve located in a central longitudinal valve-chamber formed in the rearend of the piston and operating at its movement in one direction toadmit the motive fluid to the rear side of the piston and at itsmovement in the opposite direction to place the rear end of thepiston-chamber in communication, through the internal bore of the valve,with the exhaust, substantially as described.

3. The combination of the cylinder A, the differential piston F Ftherein, forming the pressure-chamber G around the body F of the piston,and the differential valve K K K 10* cated in the valve-chamber formedin the rear portion of the piston by the central longitudinal boreLandscrew-plug J and controlling the exhaust-passage N and theinlet-passages 0, said valve being operated by the motive fluidconstantly admitted to its smaller pressure area through the passage Land alternately admitted to and exhausted from its larger pressure areathrough the passage M, substantially as described.

4:. The combination of the cylinder A, the differential piston F Ftherein provided with the passages L, M, N, O, and central longidinalbore 1, the plug J screwed into the rear end of the here I and itselfhaving a central bore into which open the inner ends of the passages O,and the tubular valve K K K operating at its movement in one directionto uncover the inner ends of the passages O and cover the inner end ofthe passage N and at its movement in the opposite direction to uncoverthe inner end of the passage N and cover the inner ends of the passagesO, and itself operated by motive fluid constantly admitted to itsforward side through the passage L and alternately admitted to andexhausted from the rear side through the passage M, substantially asdescribed.

ELIAS GUNNELL.

\Vitnesses:

WM. MAsoN, A. F. AHNER.

